Portable bridge structure



V 1944- l. B. YASSIN V PORTABLE BRIDGE'STRUQTURE 5 Sheets-Sheet 1 Filed Jan 2 6, 1943 m w R INVENTOR I NOV. 28, 1944. I YASSIN 2,363,767

PORTABLE BRIDGE STRUCTURE Filed Jan. 6; 1942' s Sheet-Sheet 2 J. .E. 5 Z 5 2/ 5 l 12 A I Nov. 28, 1944.

-l.- B. YASSIN PORTABLE BRIDGE STRUCTURE 3 sheets sheet 3 Filed Jan. 6, 1945 l INVENTOR Patented Nov. 28, 1944 UNITED STATES PATENT OFFICE.

I 2,363,767 PORTABLE BRIDGE STRUCTURE I. Ivor B. Yassin, Cambridge, Mass. Application January s, 1943, Serial No. 471,460 12 Claims. 01. 14-1) This invention is a continuation'in part of application Serial No. 178,829, filed December 8, 1937, and a continuation in partof application Serial No. 358,786, filed September 28,1940, on

Portable bridge structure.

This invention relates to portable bridge struc- .tures. The main object of the invention is to provide a portable bridge structure that may be easily placed into and moved from a position. Such a structure is to be used primarily in place of the fixed and expensive under or overpass structures used at busy crossroads or intersec-.

tions.

Another object is to provide'a bridge .structure composed of'several sections-mounted on trucks or mobile units which may be rolled into and outmoving in both directions.- This arrangementwill allow traific to enter the main highway from the crossroad or pass overthe main highway without interruption.

Another object is to provide an inexpensive and safe type of crossroad structure that approaches the safety of a Clover-leaf type of crossing without its 'great expense for constru'c' tion.

Another object; of the invention isvto provide a traffic control system at crossroads. that is 'safe because it provides unidirectional flow of traffic at all times.

Anothe object of.the invention is to provide a compac type of structure easily adapted for military or emergency use.

Other objects and advantages of this invention will become apparentas the descriptionproceeds. I do not Wish to be'limited to the specific details as described below. They are to be taken as representative structures only and not limiting;

the limitation to be only within the scope of the appendedclaims.

In the drawings: 7 v

Figure 1 shows an elevation of a double deck type of a bridge structure of. the invention positioned across the main highway to be used preterably on narrow crossroad' intersections with the main highway.

the ground emplacement means labeled A on Figure 3 for the cantilever load support truss.

- side of the parkway. The crossroad 3 is of narpurposeuse. Figure 4 shows a front elevation Figure 2 shows a diagrammatic plan view of a main highway andcrossroad intersection at which the structure of the type shown in- F'igu're 1 is employed.

Figure 3 shows an elevationof a cantilever half section unit of a single deck type of bridge struc-' ture for use at highway intersections or general of the mechanical arrangement used to effect changes in the load truss depth with the use of support bent labeled B and D of Figure 3.

Figure 5 is a side elevation section taken on Figure 4, indicated by broken line 5-5.

Figure 6 showsthe side elevation, partially sectioned, of the emplacement means of support bent labeled D and C of Figure 3.

Figure '7 is a view looking up atthe bottom of the emplacing unit labeled C on Figure 3 with the emplacement receptacle and ground deleted for clearness.

Figure 8 shows typically the side elevation of the'details of'a section of the expansible and contractivle load support truss labeled EE on Figure 3."

Figure 9 shows a section through the pivotable and detachable auxiliary pedestal used for intermediate support in the case. of long spans shown on Figure: 3.

Figure 10 shows the side elevation section of Figure '11 is. a top view partial section taken on Figure 10 indicated by broken line lI-l l.

Figure 12 shows a section of the pin connection joint of the hydraulic or pneumatic ram used for tilting or raising or lowering the bridge load support trusses from the support places o the transporting trucks.

Figure 2 shows a main highway I having a parkway 2 in its center dividing the road so that the trafiic travels in one direction only on either row width in'this case to take the portable bridge 5 of thetype shown in Figure 1, which is des1gned to carry two levels of traflic. A single level type shown in Figure 3 with two sections side by side can be used in place of the two level type forv wider crossroads 'and both modifications will be described positioned in an intersection, although onlythe double'level bridge v5 is shown thus positioned.

In the singlelevel case the crossroad 3 must be I .of sufiicient width to take two bridge sections shown inFigure 3- side by side which allow two cars to pass each otherat all points including namely at joints l2 and 14.

that purpose a short distance from the-intersection. A left turn from the main highway into the crossroad would be accomplished by crossing the crossroad under the bridge on the main highway and then-making a U turn into the other lane of the main highway at the turn 4 provided for that purpose and, if desired, making a right turn into the crossroad. It is to be noted that It is a two-way single-level roads, the single level type shown in Figure 3 can be used for wider crossroads in the same way as. the double level type and both types can be used without the pier sections l andv ll if there interference.

with my portable bridge structure and the routing of traffic as indicated above, the hazard reduc-' tion and safety resulting from a Clover-leaf the great expense of such an arrangement.

The bridge structure 5 shown on Figure 1 consists of cantilever sections 8 and 9 joined to pier sections I0 and ll respectively, by means of pin joints I2 and I4. Each section B and 9' is designed to be distributed in weight and balance so that each may be carried by one truck or other mobile mount. Each of these sections is furthermore designed to have two truss-supported road levels, 6 and 6', which are arranged one beneath the other in the same vertical plane type of crossing construction is obtained without when at ground level and side by side in the same horizontal plane when at the highest level, This arrangement is clearly shown by the arrows in Figure 2. It is to be noted that the entrance to the bridge for traffic in each direction is not obstructed. The exit in each case is beneath the entrance for the opposite direction. Adequate arches, I and I, are provided for the passage and'clearance of pleasure cars and light trucks, and the grades of roadways 6 and 6' are made capable of being negotiated by all standard cars. Due to the length of the bridge it is preferably constructed of three or four sections,'four being illustrated in Figure 1. The end sections 8 and 9 are similar and consist of upper roadbed 6 and lower roadbed 8', a continuous roadway being 66', supported by trussings suspended from girder bents l5 and I5, which are mounted at one end of movable trucks l8 of proper design to carry such truss structures. The trucks may be connected to the truss structure by hydraulic rams 3I--3i' and detachable pin joints B0, asshown in Figures 3 and 12. Also, trucks 34 may be substitutedfor truck It. In position, the bases orthe bents l5 and I5 are set into the ground in emplacements 2(Pand 23 respectively. The structure of the bent and emplacement may be as illustrated in Figures 3 to 7, inclusive. Where the cantileversection structures meet the road, ground anchor-.

ages are provided at I8, I9, 24 and 25.

The central pier sections, l0 and H, needed because of the length of the bridge, are also similar and are mounted on trucks l6, which trucks is no central parkway. In case the required span r is very long, intermediate support may be provided by auxiliary pedestal 33'shown in Figure 3.

In the case without a central parkway cross traffic will not interfere with the through traffic on the main highway and right turns toy and from the main highway may be made without Left turns, however, will haveto be made at the center of the intersection in the usual way, or by entering the side street, turn-' ing there at a rotary to enter the bridge, and crossing over to turn again at another rotary on the other side so as to make a right turn into the highway. This latter trafllc movement also gives the Clover-leaf advantage.

The double-level bridge takes up only one lane width of the crossroadand is, therefore, especially-adapted for use on narrow crossroads. At

street level the entrance and exit are one beneath the other in a vertical plane. the bridge two-level throughout would involve diflicult. awkward and costly construction; therefore, it is so designed that it becomes single level when the high point is reached.

Figure 3, in addition to showing the singlelevel type bridge with its truss-supported roadbed, support bent, auxiliary pedestal 33, emplacements, and trucks 34, shows the arrangement whereby the truss depth may be increased when the bridge is set up for use under loading and decreased for portage. Bydiminishing the height of the bent and truss and being able to up end part of the roadbed, a compactness is attained that greatly enhances the portability features and general practicability of the structure. It is obvious that the same can be achieved with the a double level bridges upper roadway support trusses, together with similar adjustments for the lower roadway support trusses, if desired.

" bridges.

4 (Figure 8).

v with adequate side trussing to carry the load,

While the double-level type is for narrow cross- The same means shown in the collapsing of the upper roadway support trusses can be employed on the mainsupport bents and side struts of the lower support trusses. though not shown, since the collapsing of the-lower trusses is of minor importance compared to the collapsing of the upper trusses. The truss depths are the main factors of the load carrying capacities of the The truss depth variationv for different loadings is a very useful function, as most often happens when a, shallow trussed bridge is ,de-

signed for one loading and then is made to carry an augmented loading as might arise in military ing change in the type of trafiic'.

The load support trusses in Figure 3 consist of upper tension chords 26 and 21, struts 29, roadbed side girders 30, and support bent B-D-C. The intermediate struts 29 are fastened at both ends by pin joints 28 and 38 The ground anchorage is indicated by A. A side guard wall,32 restrains the collapsed truss during portage. Girder 30 is joined to bent leg D by any suitable connection. Member 35 is a heavy support strut for attachment of an auxiliary section of trussed roadbed' in order to decrease the grade. The auxiliary section of trussed roadbed is 'a length of roadway and one end of which is attached to members 35 at their bases so that .the edge of this auxiliary roadbed section rests on the existing trussed To keep made by fittings 3s and 31.

have connection 38 for struts 29. f struction is typical for any joint.

roadbed 6-6 (Figures 3 and .9). The other end of the 'auxfliary roadbed section rests on the ground. A similar auxiliary roadway may be used with the roadbeds of Figure 1.

The entire cantilever unit is supported during portage by trucks 34 by means of hinged support struts 19, which are detachable or adjustable as shown by'slots, and telescopic force rams 3|3|'. Struts 19 are simple structural members, such as angles or channels, each having one pin and the other a hinged portion with a slotted end. These struts are attached by hand to pins shown on trucks 34 and bent leg D or chord 30, serving the minor purpose, when rigidly pinned as shown in Fig. 3, of preventing side sway of the bridge unit during moving In setting up or taking down the bridge unit they areiloosened and can be removed entirely or allowed to move out of interference by the jointed, slotted sec-- tion." Figure 3 shows the unit in erected position. For portability the load truss is completely collapsed within the confines of sideguard 32, and pedestal 33 is pivoted to attach under orover the bridge roadbed, or completely detached. Figure 8 shows the side elevation details of the upper tension chord 21, intermediate strut. 29,

i and roadbed side girder 30, all shown typically at EE on Figure .3. One strut 29 and" one joint 38 are shown as typical and an identical strut and connection belong on girder .30-but sufficientdisclosure is assumed-by what is shown. In Figure 3-, the drawings are to such a small scale that struts 29 are made. to meet at one point in girder 30. Actually, clearances. are preferred, and in Figure 8 this is shown by the position of 38, in line with, but away from the joint will not have 36 and 31 type fittings but will Figure 9 shows a'section' of the upper pin con nection terminal of the bridge unit with an attached pedestal and adjoining transverse roadbed. Pedestal 33 can pivotabout or be removed girder 3lJ-by means of the pin in bearallowing it to be in two .parts 3ll'and'30'. The

male fitting 36 has lug of joint 38 integral with it. Fitting 36 which is attached rigidly to'girder part 30 fits into 31, theuniting fitting attached rigidly to girder part 3|]. Fittings 36 and 31 abut against each other in a 180 degree line by construction as shown in Figure 8, and can pivot only in one direction from the 180 degree line as indicated by the cutaway clearance. Thus when the bridge is erected, parts 30 and 30 are held. rigidly by this abutment of the fittings against each other and the pinned attachment of strut 29 at joints 38 and-28.. With strut 29 and chord 21 detached, that part of the roadbed can be upended and folded over thus decreasing the length of the truss. The same can be done at the ground end of the unit, though not shown. The pedestal All roadbed joints As an al ernative or additional arrangement the chord 2 and also chord 21 may be attached to. girder at their ends in the manner showrl by Figures 10 and 11. In these figureschord- 26 is shown as provided with a slot and notches for cooperating with lugs 18 on plate 16 attached to girder 30. Plates 15 attached to chord 26 are provided with a lift bar 11. By means of the lift bar the lugs 18 may be positioned in either one of two locations in the notches, or in the slot.v

In this manner the truss maybe given two distinct depths or be substantially collapsed. Suitable struts 29 may be provided for the two depths of the truss. Although two depths of the truss by notch locations are shown, a number of depths may be provided for by the suitable number of notches appropriately located. Member 4| is the telescoping upper'part of bentof pipe cross-section. Receptacle part of 'bent, ,42, shown in Figure 5 and more clearly in Figure '1, has guide ways 43 of circular inner bear- .ing to allow sliding fit with 4|, and rectangular outer bearing for @ttachment to member 42.

Member 40 is pipe cross member for transverse support of load trusses and is welded as shown to 4|. Cover 52 is made to fit to 42 and as guard for pin joint 41. Two heavy bearing blocks 48 and 46'. support pin. 41 about which chord members 26 and 21 pivot with washer 53 strengthening end .connections as shown. Pin 49 keeps bearing block 48 in place and 48 isedge. welded.

The dotted lines show position of-chords 26 and 21 in raised position and the solid lines in lowered position, giving the extent of rotating mo- This contion. Locking lugs 54 keep the extensible member 4| in place when in-the raised position, as shown by the dotted lines. They are pulled by hand out of slots 55 as shown in solid lines, thus offering no obstruction to the up and down movements of member 4|. .|AS many slots 55 can be used as. the various adjustments of the truss call for. shown (dotted) for a shallower truss depth, thus showing three truss depths, maximum, intermediate and minimum. Pins 44 run through member 42 and bear in extensions of guide ways 43. Crank handle 45 integral with'one pin is turned, thus turning gear 5| meshed with gear 5|, both being meshed with racks 50 and 50', respectively, which are fastened-to 4|. This motion lowers extensible member 4| to the position shown, and in consequence upper chords 26 and 21 and struts 29 lie within side guard 32 of Figure 3 and indicated further in Figures 13 and 14. Slots 43 in the sides of member 4| allow movement of 4| with respect to pins '44.

The bridge section is now completely collapsed for transport, and it is necessary to release the anchorage A for the section ground terminal and anchorage C for the girder bent legs.

To release anchorage C in Figure 31 it is first necessary to pull out lock bar 56 in Figures .6 and 7 as shown by the dotted lines. The lock units consist of a casing and a slidable bar 66,

which when pushed, in as shown .p'revent th'e anchorage insert 59, a lightened steel casting,-

from sliding upwards when the compressivecolumn load of the girder bent leg 42 is applied dur ing operation of the bridge. The leg loading will be always compressive, but because of structural movements due to rolling vehicle impact loads,

.there will be momentary load application and re-] 33 may be detached or folded over to lie on the roadbed.

In this case an intermediate slot is I allow sliding of 59.

extension tongue 18.

block I3 makes-the load go to the ground. 2

is to be moved, and to der impact loads, a slight amount of play, shown in Figure 6 is allowed between the lug 56 and the top of insert casting .59, and an oleo-rubber shock absorber shown by 57, 58 and 62 is attached firmly to insert 59 by sealed outer oil cylinder 58. The shocks are then taken up by rubber discs 51 and oil cylinder 58, since in moving up cylinder 58 tends to telescope inner oil cylinder 62, which forces the oil in cylinder 58 through needle orifice 63 in to cylinder 62. Since slidable plate 65 is attached by a close sliding fit to outside of cylinder 58, its upward movement compresses rubber discs 51, which together with inner cylinder '62 are restrained at the top by plate 64 fastened firmly to girder 42. Reinforming Z-members 6i assist in proper transference of the loads through the locking bars 55 from the girder 42 to the ground through casting, 59. The Zs are cut to U-rodsdrold the rubber discs in place as shown. 7

By reason of the close sliding fit of plate65 with cylinder 58 a sudden shock will cause the two parts to seize and thus produce a compression in rubber discs 51 when cylinder 58 moves upwardly. The rubber discs then aid the oil and air in cylinders 58 and 62 in producing a shock absorber action. However, when cylinder 58 is slowly moved upwardly to withdraw insert 59 from receptacle 60, the sliding fit of plate 65 permits such'movement. The shock absorber .58,

' 62 is actually a combination of the ordinary oleopneumatic and oleo-rubber types. That is, air in the cylinder 52 is under compressionand is intended to sustain the ordinary load of the bridge. The rubber discs come into use only momentarily, when the structure is submitted to a sudden overload. Cleo-pneumatic, and oleorubber shock absorbers of the kind used here are more clearly shown on page 1560f Metal Aircraft Construction, by M. Langley, 1st ed., 1932,

' published by Gale and Polden, Ltd., of London,

England. v

To releaseanchorage A in Figure 3, it is necessary to pull out lock pins ll shown in Figure 10. These pins inserted at the ground level pass through concrete emplacement 61 which has steel receptacle 69 imbedded in it, which in turn houses The pins H thu lock tongue In firmly to the concrete emplacement. The tongue 18 has a bearing block 13 integral -with it and to which is attached handle 14. By

grasping handle 14 the tongue may be withdrawn from the receptacle 69 and made to take the position in side channels 68 shown by the broken line. Thus the terminal A' of Figure 3 is released from the ground. Sufficient clearance is left for the movements of chord 26, as tongue can be Q f shifted easily after release.

In the locked position, block." bears against collar 12 which is welded integral with side charinels 58 having oversized flanges 68', and which in turn are continuations of the web channels of roadway bed side girder 30.

Thus the load is transferred from upper chord 26 to lower chord 30 by means of union plate 76 and pins 18. In turn the load is transferred from chord 38 through'side channels 68 to collar 12,. which being restrained by bearing pressure of ,With the bridge section thus made ready for transport the raising and lowering units 3I3l are coupled by pins and adjusted by the movement of piston 3| in casing 3|, to tilt the bridge trussing and: connected roadbeds, and to take the bridge load when inserts 59 of the girder bent legs are raised by remote pumping of the oil out of cylinder 58permitting it to telescope cylinder 62. T0 erect the bridge the reverse of the procedure herein described is followed.

In order to operate the piston 3| and the shock absorber cylinder 58 a reservoir of oil is provided. A variable speed motor run from the truck power plant generator or batteries drives a variable delivery centrifugal or gear pump, capable of reversing direction, to a system of outlet valves called a selector valve, which controls the flow of oil to and from cylinders 58 and 3|. Should oil be desired in cylinder 58 for operation of the shock absorbing function of C, it is pumped by the operator to cylinder 58 and its proper v'alves closed to keep the oil in the local systems of shock absorbers CD. Should it be desired that casting insert 59 be raised,the proper valves are -opened and the oil in cylinder 58 is pumped out and back into the reservoir. The pumping out of oil tends to create a vacuum in cylinder 59 which 7 same way the rise and fall of piston ram 3| in cylinder 3| can be controlled. Each system operates independently of the other because of the selector valve and independent hydraulic lines. The necessity and obviousness of proper valves are inherent in such systems and since such hydraulic systems are common on trucks furthe illustrations are not necessary.

One of the important features ofthe invention is that the bridge sections may be rolled on their mobile mounts into and out of position all Will and assembled. in a short time. Therefore, they may be quickly put into position for weekends or holidays on roads leading out of cities to beaches or other pleasure places-or wherever it becomes known that traific will be heavy. When not needed the bridge units may then be easily removed and stored on nearby vacant land.

Being constructed of light weight, high-tensilestrength materials of the types and kinds now being used in the aircraft industry, the weight of.

- placements or bridge units. It is to be understood that a pair of trucks 34 may be considered to comprise a mobile mount or truck for an end unit, either of the single type shown in Figure 3 or the double type of Figure 1.

I claim: 1. In a portable vehicle-bridge structure of the class described, adapted for use on a road intersection, a plurality of prefabricated units com-. prising: end units, each unit having two inclinedroadways with exit emplacing means united by structural trussing of a continuous type, and being joined together with intermediate double roadway units to form a unitary vehicle-bridge structure; additional roadway lengths as continuations of existing lanes, adapted to be attached to strengthened struts of the sidetrusses of the units to vary the inclination of the roadways; the inclined roadways of the end units being attached to transverse vertical supportiframes with extensible lower sections of the columns thereof; each unit being coupled in combi-' parallel to-each other at the center of thebridge and diverting to anexit or entrance for one lane of trafiic under-the other exit-r entrance in a double-level roadway combination, one exit or entrance being at adistance from theother; said assembled vehicle-bridge structure providi'ng'an overpass crossing over a main highwaywithout obstructing the main highway. x f

2. In a portable vehicle-bridge structure of the class described, a plurality of prefabricated units comprising end units with double, inclined-roadways interlocking with intermediate units to form a unitary vehicle bridge structure, said inclinedroadways having emplacing means at the exits and being held'in relative juxtaposition by vertical 7 'side-t'russings and transverse frames; the combined inclined-roadways, side-trussing and conn'ecting transverse-frames therefor being attached to main, vertical, transverse support-frame's'with extensible columns havin emplacing'extensions movably attached at the bases of the'saidmain,-

support-frame. columns; the extensions being adaptedto be received in fixed emplacement of a prepared type and thereby supportingthe units when they are set into position on a. road and joined together; each unit being detachably mounted on a mobile-truck, so that it may be moved into or'out of position for assembly or dis-' assembly; each unit having actuating means com.- prising motivated devices at the bases of the main, support-frame columns connected to the movable column extensions for fixedly emplacing the extensions in the prepared-type emplacements when 1 in position without altering the relative positions of the bridge trussed units and the mobile truck;

Q said assembled vehicle bridge structure providing for two traifio lanes, the exit or entrance for one frames being attached to a main, vertical transverse support-frame having extensible lower sections of the support columns thereof for interlocking with fixed, prepared type road-emplacements; instrumentalities for changing the height of the upper sections of the support columns forportage; each unit being detachably mounted on a mobile-truck; and each unit having actuating means comprising motivated devices connected to the -m ova-ble column extensions at thebases of the main,-support-f rame columns for emplacing said extensions fixedly in the prepared-ty e emplacements when assembled into position, without changing the relative positions of the bridgetrussed units and the mobile-truck; said assembled vehicle-bridge structure comprising a two-f lane, double-level entry bridgewith one lane vertically over the otherattheexits or entrances and one lane beside the other in the'sarne horizontal plane when at the high point of the overs I 4. In a portable bridge structure, a side-truss supported, inclined roadbed unit, detachably carried bya mobile mount; additional roadway lengths as continuations of the existing roadbed lanes adaptedto be attachedtostrengthened struts of the side-trusses of said unit for varying the inclination of the roadbed; instrumentalities for emplacing .the unit 'fixedly into prepared-type ground emplacements for operation; contractible and extensible means for varying the depths of the side trusses of the unit for portage, said means comprising main, mutually-slidable columns con.

taining the emplacing instrumentalities in the bases thereof, and member-connected transversely to form a frame supporting the road-bed; detachable intermediate struts connecting the upper and lower chords of'the side-trusses for depth being cooperative with said slidable columns; and in strumentalities efiecting the corresponding relative movements of the upper chords of the unit side trusses, the last named structures including the main support columns having attached theupper chords and fixedly attached the lower roadbed side-chords thereto, together with the detachable chord connecting intermediate struts.

5. In a portable bridge-structure, a side truss supported, inclined roadbed unit, detachably mounted on a mobile 'truck; the side-trusses of the unit having main, support columns with lower;

extensible sections for emplacing fixedly into prepared-type emplacements and member-connected transversely to form a frame having the roadbed attached thereto; telescoping upper-column sections into receptive lower column sections; detachable intermediate struts connecting the'upper and lower chords of the side-trusses for depth being cooperative with the saidslidable columns;

the upper chords being movably attached at one endtqthe upper telescoping column sections, and

lane being at a distance from the exit or entrance of the other, both exits or entrances being in the same vertical plane; said lanes diverging by inclination from a-two-level position at the exits or entrances to a two-lane parallel position at the high point of the overpass.- 3; In a portable vehicle-bridge structure, a plu-v rality of prefabricated units comprising end units having double, inclined-roadways with end emplacing means and interlocking with intermediate units to form a unitary vehicle bridge structure;

said inclined-roadways of. each end unit being held in relative juxtaposition by connected, vertical side-trussings and transverse frames, and

I chords; said side-trusses of the unit being adjustthe opposite ends of said upper-chordsbeing slidably interlocked with the ends of the lower able in depth for different loading capacities.-

6.-In a portable bridge-structure, a side-truss supported, inclined roadbed unit, detachably mounted on a mobile-truck; the side-trusses 01' said unit having main support columns :at their greatest depths with extensible lower sections of the columns for emplacing fixedly into preparedtype emplacements and telescoping upper-col umn sections, each upper column section comprismg an inner column moving extensibly or contractibly in an outer column together with means J the combination of roadways, side-trussing and 6 to actuate said inner column slidably; a transverse bartherewith connecting the upper, inner, main-support column sections of the side-trusses and the horizontal roadbed transversely connecting the receptive outer column sections thereof; and pivotable means for the upper chords of the side-trusses attached to the inner-column sec-' tions whereby corresponding relative-movements of the upper chords may be'eifected during the telescoping action of said inner column sections.

7. In a portable bridge-structure, a side-truss supported, inclined roadbed unit, detachably mounted on a mobile-truck; the mounting :between unit and truck comprising mutually slidable members so that the relative positions of the bridge trussed unit and the mobile truck may be altered during emplacement," the side-trusses having main support-columns, connected transversely by members to form a frame supporting the roadbed, the columns having extensible lower sections for emplacing fixedly into prepared-type emplaceme-nts and telescoping upper sections linked with corresponding relatively-adjustable upper chords of the side trusses, and detachable intermediate struts connecting the upper and lower chords of the side-trusses beingcooperative with the slidable columns; sections of the lower chords also being pivotable for shortening the length of the roadbed for portage.

8. In a portable bridge-structure, a side-truss supported, inclined roadbed unit, detachably mounted on a mobile-truck; the side-trusses having main, support-columns with telescoping upper-column: sections, adjustable truss-members being cooperable with the slidable upper sections of the columns, and extensible lower-column sections for emplacing into the ground; said extensible lower-.cohrmn sections comprising elements 1 tofit into prepared-type emplacements together with-actuating means to propel said elements into my the emplacements and to withdraw the elements from-the empIace'men-ts; said actuating means also being a. shock absorber connection between the bridge unit and the emplacements.

9. In a portable bridge-structure, a side-truss supported, inclined roadbed unit,- detachably mounted on a mobile-truck; the side-trusses having main support-columns with telescoping upper column sections, adjustable truss-members being cooperable with th slidable upper sections of the columns, and extensible lower-column sections for emplacing into the ground; said extensible, lower-column sections comprising elements to fit into prepared-type emplacements and actuating means to propel the elements into the emplacements for the operation of the bridge unit and to withdraw the elements from the emplacements telescopically into the bases of the main support columns when the bridge unit is to be moved; said actuating means also efiecting dampening for the vibratory loads of the support columns under the impact loads. I

10. In a portable bridge-structure, a truss-supported bridge end unit, comprising an inclined roadbed, detachably carried by a mobile-mount; the trusses being attached to main support-columns with extensible ground anchorages at the bases of the truss main support columns,and terminal, extensible-ground anchorages at the bases :of the roadbed slope; said terminal, extensible ground anchorages comprising slidable elements to lock fixedly into theprepared-type emplacements, actuating instrumentalities to propel and withdraw the elements, and locking pins for the truss, main support-columns; said main,.supportcolumn anchorages having slidable elements to insert into the prepared-type emplacements, ac-

tuating instrumentalities to propel and withdraw the elements telescopically in the main, support column, lower fixed-sections, and locking lugs to limit the travel of the extensible elements whenemplaced. r

12, In a bridge end-structure. of the class described, a sloping roadbed unit, pivotably mounted on .a mobile-truck; said mounting between unit and: truck comprising mutually-slidable members so that the relative'positions of the bridge trussed unit and the mobile-truck may be altered during emplacement, and cooperable terminal groundanchorages for transferring all the loading from the bridge end-unit to prepared, fixed; emplacements; said terminal ground-anchorages comprising slidable extensions at the base of the'ro'adments' at the bases of the truss, main support-z bed slope with Iocking pins and. exinnsible ele columns with looking lugs; said entensions ofall ground anchorages adapted tozbe withdrawn from the emplacements telescopicallyinto-the contigunus supporting structures when: the-bridge endlmit is tilted onite-piwbtable' mommies for-nortaae. a

Q Patent No. 2,565,767.

CERTIFICATE OF comc'non.

a November 2 19111;. IVOR B. nssn.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 5, for "Portable bridge structure" read --P ortab1e bridge structures-; and second column, line 214., for "contractivle" read contractib1e-.-; page 5 first column, line 52, for "drawings are read --drawing is--; line 14.0, after the word joint and before the period insert "desired near the end of the truss"; page 11,-, first column, line 21, for

"Reinforming" read "Reinforcing"; P 5, Second mm, line 1., claim 5, for side-trussing" read --side-trussings-'; same column, 11 1 1;, l i

14., after "having" insert -movab1y'-; and that the said Letters Patent should be readwith this correction therein that the same may conforinto the record of the casein the Patent Office.

Signed and sealed this am day or May, A. D. 1915.

Leslie Frazer (Seal) Acting (iommissioner of Patents. 

